1. Field of the Invention
The present invention is generally in the field of electrical circuits, and more particularly, the invention is in the field of power converter circuits.
2. Background Art
In switched-mode power converters, for example, half-bridge or synchronous buck converters, many applications require detecting the presence of a load and/or the current polarity of a load. For example, it is often necessary to determine load current direction in battery management systems, such as in uninterruptible power supplies, or in typical electronic protection circuits. Where the power converter is, for example, a class D audio amplifier, it is often desirable to detect the presence of a speaker connected to the amplifier. As a particular example, it is desirable to provide power amplifiers with diagnostic features by detecting the presence of speakers connected to the power amplifier when implementing a multi-way speaker system in a passive frequency-dividing network.
Detecting the presence of a load and/or load polarity typically requires taking voltage or current measurements from the power converter. In one approach, load current is sensed using a resistive component, such as a shunt resistor, inserted in the load current path where the voltage drop across the resistive component is determined to measure the load current. However, because the resistive component must carry current, it will dissipate power and reduce efficiency of the power converter. The on-resistance of the power converter's high-side power switch can also be used to measure the load current. This approach is problematic as the on-resistances of power switches can vary significantly unit-to-unit, and are also strongly temperature dependent, thus leading to inaccurate results. Other approaches can use output voltages, however, it is difficult to sense voltage difference in a closed loop system.
Thus, there is a need in the art for a technique to detect the presence of a load and/or the current polarity of a load in a power converter while overcoming the drawbacks and deficiencies in the art.